HIV-1 infection of CD4-expressing cells requires interaction between envelope, CD4 and one or more chemokine receptors (seven transmembrane-spanning G protein-coupled receptors). Infection requires envelope binding to both CD4 and chemokine receptor, followed by fusion of virus and cell membrane. In the brain, infection occurs in macrophages and microglia, which express CCR5, CXCR4, and CCR3chemokine receptors. We have demonstrated that effective interaction of envelope with such receptors occurs when CD4 and chemokine receptor are expressed on the virion and envelop is expressed on the target cell. We showed that such CD4/chemokine receptor pseudovirions specifically target HIV-1 infected cells, as predicted by envelope utilization patterns by prototypic HIV-1 strains. In addition, we have used HIV-based vector pseudotypes to express transgenes in human astrocytes and neurons. Our hypothesis is that HIV-1 based vectors utilized as chemokine receptor/CD4 pseudovirus can target HIV-1- infected cells to deliver antiviral and toxicity genes to limit infection and potentially eliminate infected cellular reservoirs in the central nervous system (CNS), and that HIV-1 based vectors also allow introduction of neuroprotective genes to limit HIV-1- induced neurotoxicity. Our goal is to develop HIV-1-based pseudotype strategies to eliminate CNS reservoirs for HIV-1 and to protect neurons form effects of HIV-1 infection. To do this we will: 1) Determine the efficiency of chemokine receptor/CD4 pseudotypes (reverse pseudotypes) in transducing and killing HIV-1 infected macrophages. We will utilize reverse pseudotypes expressing a pro-apoptosis genes construct to induce apoptosis gene construct to induce apoptosis in macrophages infected with primary CNS HIV-1 isolates with different chemokine receptor utilization patterns; 2) Define the ability of HIV-1- based pseudotypes to transduce human neurons, astrocytes and macrophages to establish neuroprotective strategies against HIV-1. We will utilize pseudotype transduction of primary CNS cells to test anti-apoptosis genes as neuroprotectants; and 3) Determine the ability of pseudotypes selected from specific aims 1 & 2 to transduce primary CNS cells in vivo and to target HIV-1 infected macrophages in vivo. In collaboration with our Neuropathology core and Dr. Kerr, we will utilize a SCID-hu mouse to establish a model for HIV-1 infection of the brain to study vector transduction in vivo. The ability of HIV-based vectors to target and express in post-mitotic cells suggests new approaches for the treatment and prevention of AIDS dementia.